VARIVENT® tank bottom valves are used for shutting off pipelines at tanks or containers. Various housing connections can be welded directly into the tank bottom, flush mounted into the tank bottom wall. Simple tank shut-off valves with only one sealing surface between the tank and pipeline are available, as well as mixproof, radial sealing tank bottom valves.
Simple tank shut-off valves are used if the tank is operated with separate filling and emptying lines. It is not possible to clean the pipeline while the tank is in process.
Mixproof tank shut-off valves are used if the tank is operated with common filling and emptying lines. Mixproof separation between the pipeline and the inside of the tank allows the pipeline to be cleaned while the process in the tank continues.
In the classic variant, the mixproof tank shut-off valve separates the process in the tank from the supply to the following valve matrix, meaning that the tanks can be filled, emptied and cleaned flexibly and in parallel with one another.
For some time now, mixproof tank bottom valves have been installed horizontally on a special connection unit directly below the tank (ECO-MATRIX™). In this case, the process lines do not converge in a valve matrix, instead they are routed directly underneath the tanks in order to save space.
- The radial seal prevents switching leakage and prevents the valve disk from vibrating under high pressures
- The balancer prevents the valve disk from closing too fast when closing in the direction of product flow, thus reducing the risk of pressure hammers
- Due to the use of standard VARIVENT® actuators, this valve can be adjusted to various process parameters
- In connection with the flushing valve, the tank bottom valve can also be installed horizontally, e.g. in the new ECO-MATRIX pipe concept
Generally speaking, the mixproof variant is selected if the tank is operated with a common filling and emptying line. The mixproof valve makes it possible to clean the pipeline while the product in the tank is undergoing the required process.
When the valve is closed (non-actuated position), there are always two seals between the two fluids in the mixproof variant. If one seal is defective, the resulting leakage can be deliberately channeled out of the leakage housing into the periphery. This method enables that there cannot be any mixture between a tank and a pipeline.
Various possibilities are available for connecting VARIVENT® tank valves to the tank. Tank connection type T is used for installing valves on the tank bottom. Tank connection type U is preferred for lateral, horizontal installation of valves on the tank wall.
Cleaning the leakage chamber
Lifting actuator (type T_RC, T_RL)
Double-seat bottom valves type T_RC are equipped with a lifting actuator which enables individual lifting of a single valve disc during cleaning of the pipe or the tank. The cleaning media passes the seal of the lifted valve disc, cleans the leakage chamber and then flows out through the leakage outlet into the periphery. This way, it is possible to clean all surfaces that come into contact with the product, including the surfaces of the valve disc seals.
Spray cleaning (type T_R, T_RL)
The valves have a cleaning connection at the level of the lantern either on its own (type T_R) or additionally alongside the lifting actuator (type T_RL). This connection allows the leakage chamber to be supplied with cleaning media from an external source in order to clean this chamber (in addition to the lifting actuator) by means of an integrated spray nozzle.
After that, the cleaning media flows through the leakage outlet without pressure into the periphery. Cleaning takes place with the valve closed, which means the seal surfaces in contact are not touched during cleaning.
This way, the leakage chamber can be cleaned independently from the pipe cleaning. In addition, this allows interim flushing to occur before or after a switching procedure of the valve.
If valves are equipped with both a lifting actuator and the possibility of external spray cleaning, then spray cleaning is only used for interim flushing during the individual switching procedures, whereas thorough cleaning is performed by lifting.